samedi 25 juin 2016

Astronomers have spotted the most powerful supernova in human history. The record-breaking cosmic explosion was 570 billion times brighter than the Sun and about 200 times more powerful than a typical supernova, scientists said. The blast - known as ASASSN-15lh- is thought to be an example of a "superluminous supernova," a recently discovered type of explosion unleashed by certain stars when they die.

Astronomers spot most powerful supernova in human history

Supernovae are exploding stars at the end of their lives, providing an input of heavy elements and energy into galaxies. Some types have near-identical peak brightness, but in recent years a new class of superluminous supernovae has been found. Dong et al.y report the discovery of ASASSN-15lh (SN 2015L), the most luminous supernova yet found by some margin. It appears to originate in a large quiescent galaxy, in contrast to most super-luminous supernovae, which typically come from star-forming dwarf galaxies. The discovery will provide constraints on models of superluminous supernovae and how they affect their host galaxies.

ASAS SN 15lh is 570 billion times brighter than the Sun

Abstract

We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu,AB = –23.5 ± 0.1 and bolometric luminosity Lbol = (2.2 ± 0.2) × 1045 ergs s–1,
which is more than twice as luminous as any previously known supernova.
It has several major features characteristic of the hydrogen-poor
super-luminous supernovae (SLSNe-I), whose energy sources and
progenitors are currently poorly understood. In contrast to most
previously known SLSNe-I that reside in star-forming dwarf galaxies,
ASASSN-15lh appears to be hosted by a luminous galaxy (MK ≈ –25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 ± 0.2) × 1052 ergs, challenging the magnetar model for its engine.

"ASASSN-15lh may lead to new thinking and new observations of the whole class of superluminous supernova."

ASAS SN 15lh "superluminous" supernova explosion

The explosion, described in a study published in the Science journal, was first glimpsed in June and took place around 3.8 billion light years away. It was more than twice the brightness of the previous record-holding supernova and 20 times that of the 100 billion stars in the Milky Way. The event was spotted by two telescopes in Chile as part of an international space survey based at America's Ohio State University.

China have conducted the maiden launch of the Long March 7 rocket on Saturday. The launch took place at 12:00 UTC, which also involved the inauguration of is new Wenchang Space Launch Center, located at the Hainan Island. The main payload for this mission was a scaled-down version of a next generation crew vehicle that is expected to be recovered in Inner Mongolia after a short orbital flight.

China's Long March-7 Succeeds in Maiden Flight

Long March 7 Maiden Flight

The development of the Chang Zheng-7 (CZ-7) (Long March-7 – LM-7) launch vehicle begin in May 2010, then designated the Chang Zheng-2F/H (CZ-2F/H). The new launcher is China’s new-generation medium-lift orbital launch vehicle, developed by the China Academy of Launch Vehicle Technology (CALT).

The initial project was to be a modernized version of the CZ-2F, to be used on unmanned and manned flight missions in the China Manned Space Program. LM-7 will be mainly used for orbiting the new Tianzhou cargo vehicle for the Tiangong-2 program, which will progress into the modular Tiangong space station. Its future role will be to replace the hypergolic launchers of the LM-2, LM-3 and LM-4 rockets.

Chang Zheng-7 (CZ-7) (Long March-7 – LM-7)

Initial flights of the new launch vehicle will be classed as test launches before achieving an operational capability, at which point it will be qualified for manned launches. The new rocket is powered by the newly developed YF-100 – the first stage using two engines and strap-on boosters using a single engine each, and a YF-115 driven second stage using four engines. Both stages run on kerosene and liquid oxygen.

Three Expedition 48-49 crew members are at the Baikonur Cosmodrome awaiting the beginning of their mission in less than two weeks. Back inside the International Space Station, the orbiting crew is working on research hardware and conducting life science.

Veteran cosmonaut Anatoly Ivanishin and first time space flyers Kate Rubins from NASA and Takuya Onishi from the Japan Aerospace Exploration Agency are at their launch site counting down to a July 6 launch. The new trio will launch aboard the upgraded Soyuz MS-01 spacecraft and take a two day trip before docking to the Rassvet module.

Expedition 48 Commander Jeff Williams and cosmonauts Oleg Skripochka and Alexey Ovchinin will welcome their new crewmates July 9. After they dock and enter their new home, the new station residents will say hello to family and mission officials and then receive a safety briefing before kicking off their four-month mission.

In the meantime, Williams stowed hardware that observed how gases and liquids flow through porous media. The hardware is part of the Packed Bed Reactor Experiment that may help engineers design more efficient life support systems benefiting future space missions.

The two cosmonauts, Skripochka and Ovchinin, explored how plasmas behave when trapped in a magnetic field. The duo also looked at heart health in space and photographed Earth features to document natural and man-made changes.

Yesterday (6/24), at exactly 9:57 and 48 seconds a.m. PDT, NASA's Juno spacecraft was 5.5 million miles (8.9 million kilometers) from its July 4th appointment with Jupiter. Over the past two weeks, several milestones occurred that were key to a successful 35-minute burn of its rocket motor, which will place the robotic explorer into a polar orbit around the gas giant.

"We have over five years of spaceflight experience and only 10 days to Jupiter orbit insertion," said Rick Nybakken, Juno project manager from NASA's Jet Propulsion Laboratory in Pasadena, California. "It is a great feeling to put all the interplanetary space in the rearview mirror and have the biggest planet in the solar system in our windshield."

On June 11, Juno began transmitting to and receiving data from Earth around the clock. This constant contact will keep the mission team informed on any developments with their spacecraft within tens of minutes of it occurring. On June 20, the protective cover that shields Juno's main engine from micrometeorites and interstellar dust was opened, and the software program that will command the spacecraft through the all-important rocket burn was uplinked.

One of the important near-term events remaining on Juno's pre-burn itinerary is the pressurization of its propulsion system on June 28. The following day, all instrumentation not geared toward the successful insertion of Juno into orbit around Jupiter on July 4 will be turned off.

Jupiter Into the Unknown (NASA Juno Mission Trailer)

"If it doesn't help us get into orbit, it is shut down," said Scott Bolton, Juno's principal investigator from the Southwest Research Institute in San Antonio. "That is how critical this rocket burn is. And while we will not be getting images as we make our final approach to the planet, we have some interesting pictures of what Jupiter and its moons look like from five-plus million miles away."

The mission optical camera, JunoCam, imaged Jupiter on June 21, 2016, at a distance of 6.8 million miles (10.9 million kilometers) from the gas giant. In the image, just to the right of center is Jupiter, with its distinctive swirling bands of orange, brown and white. To the left of Jupiter (from right to left) are the planet's four largest moons -- Europa, Io, Callisto and Ganymede. Juno is approaching over Jupiter's north pole, affording the spacecraft a unique perspective on the Jovian system. Previous missions that imaged Jupiter on approach saw the system from much lower latitudes, closer to the planet's equator.

JunoCam is an outreach instrument -- its inclusion in this mission of exploration was to allow the public to come along for the ride with Juno. JunoCam’s optics were designed to acquire high-resolution views of Jupiter’s poles while the spacecraft is flying much closer to the planet. Juno will be getting closer to the cloud tops of the planet than any mission before it, and the image resolution of the massive gas giant will be the best ever taken by a spacecraft.

Image above: NASA's Juno spacecraft obtained this color view on June 21, 2016, at a distance of 6.8 million miles (10.9 million kilometers) from Jupiter. As Juno makes its initial approach, the giant planet's four largest moons -- Io, Europa, Ganymede and Callisto -- are visible, and the alternating light and dark bands of the planet's clouds are just beginning to come into view. Image Credits: NASA/JPL-Caltech/MSSS.

All of Juno’s instruments, including JunoCam, are scheduled to be turned back on approximately two days after achieving orbit. JunoCam images are expected to be returned from the spacecraft for processing and release to the public starting in late August or early September.

"This image is the start of something great," said Bolton. "In the future we will see Jupiter's polar auroras from a new perspective. We will see details in rolling bands of orange and white clouds like never before, and even the Great Red Spot.

JPL manages the Juno mission for the principal investigator, Scott Bolton, of Southwest Research Institute in San Antonio. Juno is part of NASA's New Frontiers Program, which is managed at NASA's Marshall Space Flight Center in Huntsville, Alabama, for NASA's Science Mission Directorate. Lockheed Martin Space Systems, Denver, built the spacecraft. The California Institute of Technology in Pasadena, California, manages JPL for NASA.

vendredi 24 juin 2016

United Launch Alliance Successfully Launches MUOS-5 Satellite for the U.S Air Force and U.S. Navy, MUOS-5 completes the five-satellite constellation and acts as an on-orbit spare.

Atlas V Rocket Launches MUOS-5 satellite for the U.S. Navy

A United Launch Alliance (ULA) Atlas V rocket successfully launched the MUOS-5 satellite for the U.S. Navy. The rocket lifted off from Space Launch Complex-41 June 24 at 10:30 a.m. EDT.

MUOS-5 is the final satellite in the five-satellite constellation, which provides warfighters with significantly improved and assured communications worldwide.

ULA Atlas V launches MUOS-5 Satellite for the U.S. Navy

“We are honored to deliver the final satellite in the MUOS constellation for the U.S. Navy,” said Laura Maginnis, ULA vice president, Custom Services. “Congratulations to our navy, air force and Lockheed Martin mission partners on yet another successful launch that provides our warfighters with enhanced communications capabilities to safely and effectively conduct their missions around the globe.”

Atlas V / MUOS-5 Mission poster

The mission was ULA’s fifth launch in 2016 and 108th launch since the company formed in 2006. MUOS-5 was the seventh mission to be launched aboard an Atlas V Evolved Expendable Launch Vehicle (EELV) 551 configuration vehicle, which includes a 5-meter diameter payload fairing and five solid rocket boosters. The Atlas booster for this mission was powered by the RD AMROSS RD-180 engine and the Centaur upper stage was powered by the Aerojet Rocketdyne RL10C-1 engine.

“I am so proud of the team for all their hard work and commitment to 100 percent mission success,” Maginnis said. “It is amazing to deliver our second national security payload from the Cape in just two weeks. I know this success is due to our amazing people who make the remarkable look routine.”

ULA's next launch is the Atlas V NROL-61 mission for the National Reconnaissance Office, scheduled for July 28 from Space Launch Complex-41 at Cape Canaveral Air Force Station, Florida.

An artist's concept of MUOS 5 in orbit. Image Credit: U.S. Navy

The EELV program was established by the U.S. Air Force to provide assured access to space for Department of Defense and other government payloads. The commercially developed EELV program supports the full range of government mission requirements, while delivering on schedule and providing significant cost savings over the heritage launch systems.

With more than a century of combined heritage, United Launch Alliance is the nation’s most experienced and reliable launch service provider. ULA has successfully delivered more than 100 satellites to orbit that provide critical capabilities for troops in the field, aid meteorologists in tracking severe weather, enable personal device-based GPS navigation and unlock the mysteries of our solar system.

This NASA/ESA Hubble Space Telescope image shows the star cluster NGC 1854, a gathering of red, white and blue stars in the southern constellation of Dorado (The Dolphinfish). NGC 1854 is located about 135,000 light-years away in the Large Magellanic Cloud (LMC), one of our closest cosmic neighbors and a satellite galaxy of the Milky Way.

The LMC is a hotbed of vigorous star formation. Rich in interstellar gas and dust, the galaxy is home to approximately 60 globular clusters and 700 open clusters. These clusters are frequently the subject of astronomical research, as the Large Magellanic Cloud and its little sister, the Small Magellanic Cloud, are the only systems known to contain clusters at all stages of evolution. Hubble is often used to study these clusters as its extremely high-resolution cameras can resolve individual stars, even at the clusters’ crowded cores, revealing their mass, size and degree of evolution.

A Russian cargo ship currently docked to the International Space Station will undock for a short test flight on Friday, July 1. NASA Television coverage will begin at 1:15 a.m. EDT.

The Progress 62 cargo ship will automatically undock from the Pirs Docking Compartment of the space station and manually be guided in to re-dock. The maneuver will begin with undocking at 1:36 a.m. and take approximately 30 minutes, with re-docking planned for 2:10 a.m.

Image above: The unpiloted ISS Progress 62 Russian cargo ship is seen docked to the Pirs docking compartment of the International Space Station. The spacecraft launched from the Baikonur Cosmodrome in Kazakhstan Dec. 21, 2015 and docked two days later. Image Credit: NASA.

This activity will test a newly installed manual docking system inside the station’s Russian segment. The resupply ship will back away to a distance of about 600 feet (about 183 meters) from the station, at which point Expedition 48 cosmonauts Alexey Ovchinin and Oleg Skripochka of the Russian space agency Roscosmos will take manual control of the spacecraft. They will use a workstation in the Zvezda Service Module to “fly” the Progress back to a linkup with Pirs.

The system test will include verification of software and a new signal converter incorporated in the upgraded manual docking system for future use in both Progress and piloted Soyuz vehicles in the unlikely event the “Kurs” automated rendezvous in either craft encounters a problem.

Progress 62 arrived at the station Dec. 23, 2015 with more than three tons of food, fuel and supplies, and will undock for the final time at 11:48 p.m. Saturday, July 2. The spacecraft, loaded with trash, will be deorbited by Russian flight controllers to burn up in the Earth’s atmosphere over the Pacific Ocean.

It gives a birds-eye-view onto the layered terraces in Seth (bottom left) and Babi (top left), with hints of the smooth dust-covered Ash region towards the bottom left corner.

The boulder-strewn neck region, Hapi, lies in the centre of the image. Following the course of the neck ‘up’ towards the top of the frame, the boundary between Hapi and Aker is encountered.

The view of the small lobe, to the right of the scene, is dominated by the dusty surfaces of Ma’at, and casts an impressive shadow over the landscape below.

Image above: OSIRIS narrow-angle camera image taken on 8 June 2016, when Rosetta was 29.7 km from the centre of Comet 67P/Churyumov–Gerasimenko. The scale is 0.53 m/pixel and the image measures about 1.1 km across. Image Credits: ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA.

An OSIRIS ‘image of the day’ released this week (above) provides a complementary view of the biggest terrace in Seth, which – following the Egyptian naming convention on the comet – scientists have nicknamed Aswan.

Aswan boasts a variety of geomorphological features, such as steep, layered and fractured walls that contrast against the relatively smooth and flat, dust-covered terrace that was once considered a possible landing site for Philae.

Along the cliff edge multiple arch-shaped features can be seen; they likely represent an eroding margin linked to sublimation and fracturing.

A handful of large boulders are also present amongst many smaller ones; to give a sense of scale, the majority of boulders seen in this image are around 2 m wide or larger, with the large boulder situated close to the cliff measuring just over 19 m across.

On Saturday 25 June, the LISA Technology Package (LTP) – a European payload on ESA's LISA Pathfinder – completes its nominal operations phase, passing the baton to the Disturbance Reduction System, an additional experiment provided by NASA. This won't be the last time the European experiment is run – the recently approved mission extension will see the LTP back in action for seven months starting in November this year.

LISA Pathfinder operations. Credit: ESA/C. Carreau

After over three months of outstanding scientific experiments, the first operations phase of the LISA Pathfinder mission is coming to an end. The conclusion of this part of the mission is foreseen for 10:00 CEST (08:00 UTC) on Saturday, 25 June 2016.

Launched on 3 December 2015, LISA Pathfinder is a technology demonstrator, testing instruments and methods to observe gravitational waves – fluctuations in the fabric of spacetime – from space.

The spacecraft reached its operational orbit around the Lagrange point L1 – 1.5 million km away from Earth towards the Sun – at the end of January and, following a number of crucial milestones during the commissioning phase, the science mission began on 1 March.

At the core of the spacecraft are two test masses – a pair of identical gold-platinum cubes, measuring 46 mm and with a mass of 2 kg each. As recently announced, the mission reached, and very soon exceeded, its goal: placing the two test masses in the most precise freefall ever.

This was achieved by measuring the position and orientation of the test masses – whose motion is continually perturbed by external and internal forces – with a laser interferometer, and by subsequently manoeuvring the spacecraft around them to be constantly centred on one of the cubes, shielding the test masses without touching them.

LISA Pathfinder results. Credit: ESA/LISA Pathfinder Collaboration

The team's first results, based on just two months of operations, show that the mission has already obtained a control on the test masses comparable to that needed to build a future space-borne observatory of gravitational waves. A paper reporting the results is published in Physical Review Letters.

"During the last few weeks, we improved the performance even further than detailed in the paper," says Paul McNamara, LISA Pathfinder Project Scientist at ESA. "We couldn't be happier about the mission's outcome."

Until today, the spacecraft has been adjusting its position using several sets of cold-gas thrusters that are applied on three of the outer panels of the science module and are capable of applying forces of 1–100 micronewtons. The cold-gas thrusters work in tandem with the LISA Technology Package (LTP), the mission's core payload, which was developed by ESA and several institutes, industry and space agencies from ESA member states.

This first phase in the mission comprised about 100 days of operations, as well as 15 days dedicated to station-keeping manoeuvres – these correct the spacecraft orbit once every one to two weeks.

From 26 June, the mission will start running the Disturbance Reduction System (DRS) payload, a separate experiment contributed by the US. This experiment receives measurement input from the test masses and interferometer that are part of the LTP, but will then use its own drag-free control software and two clusters of micronewton thrusters, mounted on two opposite panels of the science module, to control the position and attitude of the spacecraft.

Colloid thrusters. Credit: ESA/NASA/JPL-Caltech

Based on colloidal micronewton thrusters, which generate propulsion by charging small drops of liquid and accelerating them through an electric field, the DRS experiment contributes to the mission by validating additional technology for future drag-free spacecraft.

After two weeks of commissioning, the operations phase of the DRS will last until the end of October. The LTP team will return for one week in early August to continue the long-term monitoring of their experiment and to facilitate some cross-calibration with the DRS experiment.

An extended mission, approved by ESA's Science Programme Committee at their 21-22 June meeting, will begin on 1 November, for seven months. During this period the team will further investigate the performance of the LTP at low frequencies – of particular interest in the context of a future space-based gravitational-wave observatory – as well as testing some experimental operational modes.

"Although we won't be working with our LISA Technology Package for most of the next few months while the Disturbance Reduction System experiment is running, we do have plenty of excellent data that we'll be examining in great detail," says Paul. "But there's no doubt that we'll be looking forward to seeing how far we can go with LISA Pathfinder when we start the extended mission later this year."

Notes for Editors:

LISA Pathfinder is an ESA mission with important contributions from its member states and NASA.

The LISA Technology Package payload has been delivered by several national funding agencies and ESA, in particular: Italy (ASI); Germany (DLR); the United Kingdom (UKSA); France (CNES); Spain (CDTI); Switzerland (SSO); and the Netherlands (SRON). LISA Pathfinder also carries the Disturbance Reduction System payload, provided by NASA.

jeudi 23 juin 2016

Understanding how fire spreads in a microgravity environment is critical to the safety of astronauts who live and work in space. And while NASA has conducted studies aboard the space shuttle and International Space Station, risks to the crew have forced these experiments to be limited in size and scope. Fire safety will be a critical element as NASA progresses on the journey to Mars and begins to investigate deep space habitats for long duration missions.

The first Spacecraft Fire Experiment (Saffire-I) was the beginning of a three-part experiment to be conducted over the course of three flights of Orbital ATK’s Cygnus vehicle to investigate large-scale flame spread and material flammability limits in long duration microgravity.

The Saffire-I experiment enclosure was approximately half a meter wide by 1 meter deep by 1.3 meter long and consisted of a flow duct and avionics bay. Inside the flow duct, the cotton-fiberglass blend burn sample measured 0.4 m wide by 1 meter long. When commanded by Orbital ATK and Saffire ground controllers operating from Dulles, Virginia, it was ignited by a hot wire. Previous to this experiment, the largest fire experiment that had been conducted in space is about the size of an index card.

Saffire-I Experiment Burns in Space

Video above: Understanding how fire spreads in a microgravity environment is critical to the safety of astronauts who are on the #JourneyToMars. This compilation of images shows Saffire-I, an experiment that burned a cotton-fiberglass blend of material to see how it behaved in space. The green LED light flashes were used to show contrast to observe smoke patterns as the material was burning. Image Credit: NASA.

After the experiment was ignited, the Cygnus continued to orbit Earth for six days as it transmitted high-resolution imagery and data from the Saffire experiment. Following complete data transmission, the Cygnus spacecraft completed its mission with a destructive entry into the Earth’s atmosphere.

Disruptive technologies have often changed the course of history, breaking the status quo and unlocking possibilities that have yet to be imagined. Building on a history of upgrading and maintaining assets in space, NASA is developing a new capability while creating a paradigm-shift: robotic satellite servicing.

In May, NASA officially moved forward with plans to execute the ambitious, technology-rich Restore-L mission, an endeavor to launch a robotic spacecraft in 2020 to refuel a live satellite. The mission – the first of its kind in low-Earth orbit - will demonstrate that a carefully curated suite of satellite-servicing technologies are fully operational. The current candidate client for this venture is Landsat 7, a government-owned satellite in low-Earth orbit.

Beyond refueling, the Restore-L mission also carries another, weighty objective: to test other crosscutting technologies that have applications for several critical upcoming NASA missions. As the Restore-L servicer rendezvous with, grasps, refuels, and relocates a client spacecraft, NASA will be checking important items off of its technology checklist that puts humans closer to Mars exploration.

Restore-L technologies include an autonomous relative navigation system with supporting avionics, and dexterous robotic arms and software. The suite is completed by a tool drive that supports a collection of sophisticated robotic tools for robotic spacecraft refueling, and a propellant transfer system that delivers measured amounts of fuel at the proper temperature, rate, and pressure.

The robotic vehicle of NASA’s Asteroid Redirect Mission directly leverages Restore-L’s autonomous rendezvous system, avionics, dexterous robotics and software, and tool drive and other systems. This mission, along with the Wide-Field Infrared Survey Telescope (WFIRST) observatory, is being designed to be refuelable.

NASA's second, equally important objective for Restore-L is to infuse its technologies to domestic commercial entities to help jumpstart a new, competitive industry in robotic satellite servicing, an area ripe with possibility.

"Restore-L effectively breaks the paradigm of one-and-done spacecraft" says Frank Cepollina, veteran leader of the five crewed servicing missions to the Hubble Space Telescope. Cepollina now serves as the associate director of the Satellite Servicing Capabilities Office (SSCO), the team that first conceived of the Restore-L concept and developed its technology portfolio.

"It introduces new ways to robotically manage, upgrade and prolong the
lifespans of our costly orbiting national assets. By doing so, Restore-L
opens up expanded options for more resilient, efficient and
cost-effective operations in space," says Cepollina.

Image above: An engineering design unit of the NASA Servicing Arm, which will be used for the Restore-L mission, stands in the Robotics Operations Center at NASA’s Goddard Space Flight Center. Image Credits: NASA/Chris Gunn.

Currently, spacecraft launch to space with a finite amount of fuel, their lifespans restricted by the amount of propellant within their metal spacecraft buses at launch. A refueling capability in space, offered by future propellant-delivery spacecraft similar to Restore-L, could provide satellite owners the ability to manage, maintain, and save their most valuable assets in space.

American industry appears eager to offer such services and has expressed strong interest in this burgeoning field. NASA's transfer of Restore-L technologies to interested domestic entities could help spur the arrival of such commercial life extension and repair offerings. The Restore-L mission could also help decrease the risk for future servicing ventures and establish a global precedence for safe rendezvous operations in orbit.

Restore-L’s technologies are foundational for other ambitious objectives beyond refueling. “You cannot entirely forecast how the aerospace community will run with new, capability-building servicing technologies, but we can predict likely short-term innovations,” says Benjamin Reed, deputy project manager for SSCO.

"With robotic servicing on the table, satellite owners can extend the lifespan of satellites that are running low on fuel, reaping additional years of service – and revenue – from their initial investment. If a solar array or a communications antenna fails to deploy, a servicer with inspection cameras and the right repair tools could help recover the asset that otherwise would have been lost. The loss of an anticipated revenue or data stream can be devastating,” Reed says.

Servicing capabilities could help satellite owners better manage their space assets in innovative ways. This could include launching a spacecraft with a half-empty fuel tank and allotting the saved weight to mission-specific instruments. “Dependable robotic satellite servicing unlocks countless opportunities,” Reed says.

Pluto’s largest moon, Charon, is home to an unusual canyon system that’s far longer and deeper than the Grand Canyon.

The inset above magnifies a portion of the eastern limb in the global view of Charon at left, imaged by NASA’s New Horizons spacecraft several hours before its closest approach on July 14, 2015. A deep canyon informally named Argo Chasma is seen grazing the limb. The section of it seen here measures approximately 185 miles (300 kilometers) long. As far as New Horizons scientists can tell, Argo’s total length is approximately 430 miles (700 kilometers) long – for comparison, Arizona’s Grand Canyon is 280 miles (450 kilometers) long.

At this fortuitous viewing angle the canyon is seen edge-on, and at the northern end of the canyon its depth can be easily gauged. Based on this and other images taken around the same time, New Horizons scientists estimate Argo Chasma to be as deep as 5.5 miles (9 kilometers), which is more than five times the depth of the Grand Canyon. There appear to be locations along the canyon’s length where sheer cliffs reaching several miles high occur, and which could potentially rival Verona Rupes on Uranus’ moon Miranda (which is at least 3 miles, or 5 kilometers, high) for the title of tallest known cliff face in the solar system.

The image was obtained by New Horizons’ Long Range Reconnaissance Imager (LORRI) at a resolution of approximately 1.45 miles (2.33 kilometers) per pixel. It was taken at a range of approximately 289,000 miles (466,000 kilometers) from Charon, 9 hours and 22 minutes before New Horizons’ closest approach to Charon on July 14, 2015.

New images obtained on May 16, 2016, by NASA's Hubble Space Telescope confirm the presence of a dark vortex in the atmosphere of Neptune. Though similar features were seen during the Voyager 2 flyby of Neptune in 1989 and by the Hubble Space Telescope in 1994, this vortex is the first one observed on Neptune in the 21st century.

The discovery was announced on May 17, 2016, in a Central Bureau for Astronomical Telegrams (CBAT) electronic telegram by University of California at Berkeley research astronomer Mike Wong, who led the team that analyzed the Hubble data.

Neptune's dark vortices are high-pressure systems and are usually accompanied by bright "companion clouds," which are also now visible on the distant planet. The bright clouds form when the flow of ambient air is perturbed and diverted upward over the dark vortex, causing gases to likely freeze into methane ice crystals.

"Dark vortices coast through the atmosphere like huge, lens-shaped gaseous mountains," Wong said. "And the companion clouds are similar to so-called orographic clouds that appear as pancake-shaped features lingering over mountains on Earth."

Beginning in July 2015, bright clouds were again seen on Neptune by several observers, from amateurs to astronomers at the W. M. Keck Observatory in Hawaii. Astronomers suspected that these clouds might be bright companion clouds following an unseen dark vortex. Neptune's dark vortices are typically only seen at blue wavelengths, and only Hubble has the high resolution required for seeing them on distant Neptune.

Image above: This new Hubble Space Telescope image confirms the presence of a dark vortex in the atmosphere of Neptune. The full visible-light image at left shows that the dark feature resides near and below a patch of bright clouds in the planet's southern hemisphere. The full-color image at top right is a close-up of the complex feature. The vortex is a high-pressure system. The image at bottom right shows that the vortex is best seen at blue wavelengths Image Credits: NASA, ESA, and M.H. Wong and J. Tollefson (UC Berkeley).

In September 2015, the Outer Planet Atmospheres Legacy (OPAL) program, a long-term Hubble Space Telescope project that annually captures global maps of the outer planets, revealed a dark spot close to the location of the bright clouds, which had been tracked from the ground. By viewing the vortex a second time, the new Hubble images confirm that OPAL really detected a long-lived feature. The new data enabled the team to create a higher-quality map of the vortex and its surroundings.

Neptune's dark vortices have exhibited surprising diversity over the years, in terms of size, shape, and stability (they meander in latitude, and sometimes speed up or slow down). They also come and go on much shorter timescales compared to similar anticyclones seen on Jupiter; large storms on Jupiter evolve over decades.

Planetary astronomers hope to better understand how dark vortices originate, what controls their drifts and oscillations, how they interact with the environment, and how they eventually dissipate, according to UC Berkeley doctoral student Joshua Tollefson, who was recently awarded a prestigious NASA Earth and Space Science Fellowship to study Neptune's atmosphere. Measuring the evolution of the new dark vortex will extend knowledge of both the dark vortices themselves, as well as the structure and dynamics of the surrounding atmosphere.

Image above: Artist’s impression of the star S2 passing very close to the supermassive black hole at the centre of the Milky Way.

A European team of astronomers have used the new GRAVITY instrument at ESO’s Very Large Telescope to obtain exciting observations of the centre of the Milky Way by combining light from all four of the 8.2-metre Unit Telescopes for the first time. These results provide a taste of the groundbreaking science that GRAVITY will produce as it probes the extremely strong gravitational fields close to the central supermassive black hole and tests Einstein’s general relativity.

The GRAVITY instrument is now operating with the four 8.2-metre Unit Telescopes of ESO’s Very Large Telescope (VLT), and even from early test results it is already clear that it will soon be producing world-class science.

The centre of the Milky Way

GRAVITY is part of the VLT Interferometer. By combining light from the four telescopes it can achieve the same spatial resolution and precision in measuring positions as a telescope of up to 130 metres in diameter. The corresponding gains in resolving power and positional accuracy — a factor of 15 over the individual 8.2-metre VLT Unit Telescopes — will enable GRAVITY to make amazingly accurate measurements of astronomical objects.

One of GRAVITY’s primary goals is to make detailed observations of the surroundings of the 4 million solar mass black hole at the very centre of the Milky Way [1]. Although the position and mass of the black hole have been known since 2002, by making precision measurements of the motions of stars orbiting it, GRAVITY will allow astronomers to probe the gravitational field around the black hole in unprecedented detail, providing a unique test of Einstein’s general theory of relativity.

Video above: Artist’s impression of the star S2 passing very close to the supermassive black hole at the centre of the Milky Way.

In this regard, the first observations with GRAVITY are already very exciting. The GRAVITY team [2] has used the instrument to observe a star known as S2 as it orbits the black hole at the centre of our galaxy with a period of only 16 years. These tests have impressively demonstrated GRAVITY’s sensitivity as it was able to see this faint star in just a few minutes of observation.

The team will soon be able to obtain ultra-precise positions of the orbiting star, equivalent to measuring the position of an object on the Moon with centimetre precision. That will enable them to determine whether the motion around the black hole follows the predictions of Einstein’s general relativity — or not. The new observations show that the Galactic Centre is as ideal a laboratory as one can hope for.

Animation of the path of a light ray through GRAVITY

"It was a fantastic moment for the whole team when the light from the star interfered for the first time — after eight years of hard work," says GRAVITY’s lead scientist Frank Eisenhauer from the Max Planck Institute for Extraterrestrial Physics in Garching, Germany. "First we actively stabilised the interference on a bright nearby star, and then only a few minutes later we could really see the interference from the faint star — to a lot of high-fives.” At first glance neither the reference star nor the orbiting star have massive companions that would complicate the observations and analysis. "They are ideal probes," explains Eisenhauer.

This early indication of success does not come a moment too soon. In 2018 the S2 star will be at its closest to the black hole, just 17 light-hours away from it and travelling at almost 30 million kilometres per hour, or 2.5% of the speed of light. At this distance the effects due to general relativity will be most pronounced and GRAVITY observations will yield their most important results [3]. This opportunity will not be repeated for another 16 years.

Notes:

[1] The centre of the Milky Way, our home galaxy, lies on the sky in the constellation of Sagittarius (The Archer) and is some 25 000 light-years distant from Earth.

[2] The GRAVITY consortium consists of: the Max Planck Institutes for Extraterrestrial Physics (MPE) and Astronomy (MPIA), LESIA of Paris Observatory and IPAG of Université Grenoble Alpes/CNRS, the University of Cologne, the Centro Multidisciplinar de Astrofísica Lisbon and Porto (SIM), and ESO.

[3] The team will, for the first time, be able to measure two relativistic effects for a star orbiting a massive black hole — the gravitational redshift and the precession of the pericentre. The redshift arises because light from the star has to move against the strong gravitational field of the massive black hole in order to escape into the Universe. As it does so it loses energy, which manifests as a redshift of the light. The second effect applies to the star’s orbit and leads to a deviation from a perfect ellipse. The orientation of the ellipse rotates by around half a degree in the orbital plane when the star passes close to the black hole. The same effect has been observed for Mercury's orbit around the Sun, where it is about 6500 times weaker per orbit than in the extreme vicinity of the black hole. But the larger distance makes it much harder to observe in the Galactic Centre than in the Solar System.

More information:

ESO is the foremost intergovernmental astronomy organisation in Europe and the world’s most productive ground-based astronomical observatory by far. It is supported by 16 countries: Austria, Belgium, Brazil, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom, along with the host state of Chile. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in promoting and organising cooperation in astronomical research. ESO operates three unique world-class observing sites in Chile: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope, the world’s most advanced visible-light astronomical observatory and two survey telescopes. VISTA works in the infrared and is the world’s largest survey telescope and the VLT Survey Telescope is the largest telescope designed to exclusively survey the skies in visible light. ESO is a major partner in ALMA, the largest astronomical project in existence. And on Cerro Armazones, close to Paranal, ESO is building the 39-metre European Extremely Large Telescope, the E-ELT, which will become “the world’s biggest eye on the sky”.

Scientists have discovered an unexpected mineral in a rock sample at Gale Crater on Mars, a finding that may alter our understanding of how the planet evolved.

NASA's Mars Science Laboratory rover, Curiosity, has been exploring sedimentary rocks within Gale Crater since landing in August 2012. In July 2015, on Sol 1060 (the number of Martian days since landing), the rover collected powder drilled from rock at a location named "Buckskin." Analyzing data from an X-ray diffraction instrument on the rover that identifies minerals, scientists detected significant amounts of a silica mineral called tridymite.

This detection was a surprise to the scientists, because tridymite is generally associated with silicic volcanism, which is known on Earth but was not thought to be important or even present on Mars.

The discovery of tridymite might induce scientists to rethink the volcanic history of Mars, suggesting that the planet once had explosive volcanoes that led to the presence of the mineral.

Image above: This low-angle self-portrait of NASA's Curiosity Mars rover shows the vehicle at the site from which it reached down to drill into a rock target called "Buckskin." Bright powder from that July 30, 2015, drilling is visible in the foreground. Image Credits: NASA/JPL-Caltech/MSSS.

Scientists in the Astromaterials Research and Exploration Science (ARES) Division at NASA's Johnson Space Center in Houston led the study. A paper on the team's findings has been published in the Proceedings of the National Academy of Sciences.

"On Earth, tridymite is formed at high temperatures in an explosive process called silicic volcanism. Mount St. Helens, the active volcano in Washington State, and the Satsuma-Iwojima volcano in Japan are examples of such volcanoes. The combination of high silica content and extremely high temperatures in the volcanoes creates tridymite," said Richard Morris, NASA planetary scientist at Johnson and lead author of the paper. "The tridymite was incorporated into 'Lake Gale' mudstone at Buckskin as sediment from erosion of silicic volcanic rocks."

The paper also will stimulate scientists to re-examine the way tridymite forms. The authors examined terrestrial evidence that tridymite could form at low temperatures from geologically reasonable processes and not imply silicic volcanism. They found none. Researchers will need to look for ways that it could form at lower temperatures.

"I always tell fellow planetary scientists to expect the unexpected on Mars," said Doug Ming, ARES chief scientist at Johnson and co-author of the paper. "The discovery of tridymite was completely unexpected. This discovery now begs the question of whether Mars experienced a much more violent and explosive volcanic history during the early evolution of the planet than previously thought."

NASA's Jet Propulsion Laboratory, a division of Caltech in Pasadena, California, built the rover and manages the Curiosity mission for NASA's Science Mission Directorate, Washington. For more about Curiosity, visit: http://mars.nasa.gov/msl/

Ending gloriously with a colorful flight formation from the Spanish Patrulla Águila, Bertrand Piccard landed in Seville at 5:38AM UTC, 7:38AM CET, 1:38AM EDT on June 23rd after completing the crossing of the Atlantic Ocean.

Spanish Patrulla Águila welcome Si2

Bertrand Piccard has surpassed aviation with this flight by adding an extra twist to this challenge of crossing the Atlantic Ocean. Just like Charles Lindbergh, Bertrand Piccard flew across the Atlantic Ocean, but didn’t choose the easiest way to get there. Himself, André Borschberg and the Solar Impulse team needed an extra challenge: to cross the Atlantic Ocean without a single drop of fuel. This is not a first for aviation, but definitely a first for clean technology.

A beautiful flight that has countlessly left Bertrand in awe at the vast expanse of the Atlantic Ocean - encountering oil tankers, islands, whales, icebergs, and an abundance of water. This flight is Bertrand Piccard’s longest flight with Si2 - reaching a total flight time of 71 hours and 8 minutes to make it across the pond to Europe on the round-the-world solar flights.

Bertrand Piccard, pilot of this flight

His solar brother, André Borschberg, joined the mission engineers at the Mission Control Center in Monaco during the first half of the flight to help plan and follow the flight as closely as possible. They had a few chats over the satcom where André shared his experience from his 117 hour flight. Then he had to race off to Seville, Spain to get the ground crew operations underway, preparing for Bertrand Piccard’s landing. Michèle Piccard, Bertrand’s partner, also passed by the Mission Control Center for two days during the flight to watch the flight from up close and support Bertrand.

Solar Impulse Airplane - Leg 15 - Flight New York to Seville

At 6:30AM UTC, 8:30AM CET, 2:30AM EDT on June 20th, Bertrand Piccard took off from New York City. Thanks to the meticulous work from the Mission Control Center and our weather specialists, they were able to identify a narrow window, bypassing a cold front that was situated in the middle of the Atlantic. We were lucky because it only took the mission engineers nine days to find a weather window to cross the Atlantic Ocean - a lot less time than anyone expected for the volatile Atlantic Ocean. This window opened up to a fantastic path that gave way to this flight to the beautiful Spanish city, Seville.

Si2 landing at Seville

What’s next?

We have now accomplished the crossing of both the Pacific and the Atlantic, the world’s two biggest oceans. This means that 90% of the Round-The-World journey is already behind us. That number sounds completely crazy!

What lies ahead for the remaining 10%? Still a mystery. What we know is that we’ll be staying a few days in Seville – not sure about the organization of a public day yet, we’ll keep you posted – and then fly to Egypt or Greece. To get the latest updates, just give us your email address here and we’ll be sure to send them to you as soon as something new comes up: http://www.solarimpulse.com/subscribe

In another three flights or so we’ll be landing in the summer heat of Abu Dhabi. We’re really beginning to feel like success is at our fingertips! Success will be measured by the number of kilometres we’ve accomplished, but most of all by the number of people we will have inspired to follow their dreams and make the world a better place. Help us by spreading the #futureisclean message!

mercredi 22 juin 2016

Some 3.9 billion years ago in the heart of a distant galaxy, the intense tidal pull of a monster black hole shredded a star that passed too close. When X-rays produced in this event first reached Earth on March 28, 2011, they were detected by NASA's Swift satellite, which notified astronomers around the world. Within days, scientists concluded that the outburst, now known as Swift J1644+57, represented both the tidal disruption of a star and the sudden flare-up of a previously inactive black hole.

Now astronomers using archival observations from Swift, the European Space Agency's (ESA) XMM-Newton observatory and the Japan-led Suzaku satellite have identified the reflections of X-ray flares erupting during the event. Led by Erin Kara, a postdoctoral researcher at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the University of Maryland, College Park (UMCP), the team has used these light echoes, or reverberations, to map the flow of gas near a newly awakened black hole for the first time.

"While we don't yet understand what causes X-ray flares near the black hole, we know that when one occurs we can detect its echo a couple of minutes later, once the light has reached and illuminated parts of the flow," Kara explained. "This technique, called X-ray reverberation mapping, has been previously used to explore stable disks around black holes, but this is the first time we've applied it to a newly formed disk produced by a tidal disruption."

Image above: In this artist's rendering, a thick accretion disk has formed around a supermassive black hole following the tidal disruption of a star that wandered too close. Stellar debris has fallen toward the black hole and collected into a thick chaotic disk of hot gas. Flashes of X-ray light near the center of the disk result in light echoes that allow astronomers to map the structure of the funnel-like flow, revealing for the first time strong gravity effects around a normally quiescent black hole. Image Credits: NASA/Swift/Aurore Simonnet, Sonoma State University.

Stellar debris falling toward a black hole collects into a rotating structure called an accretion disk. There the gas is compressed and heated to millions of degrees before it eventually spills over the black hole's event horizon, the point beyond which nothing can escape and astronomers cannot observe. The Swift J1644+57 accretion disk was thicker, more turbulent and more chaotic than stable disks, which have had time to settle down into an orderly routine. The researchers present the findings in a paper published online in the journal Nature on Wed., June 22.

One surprise from the study is that high-energy X-rays arise from the inner part of the disk. Astronomers had thought most of this emission originated from a narrow jet of particles accelerated to near the speed of light. In blazars, the most luminous galaxy class powered by supermassive black holes, jets produce most of the highest-energy emission.

"We do see a jet from Swift J1644, but the X-rays are coming from a compact region near the black hole at the base of a steep funnel of inflowing gas we're looking down into," said co-author Lixin Dai, a postdoctoral researcher at UMCP. "The gas producing the echoes is itself flowing outward along the surface of the funnel at speeds up to half the speed of light."

X-rays originating near the black hole excite iron ions in the whirling gas, causing them to fluoresce with a distinctive high-energy glow called iron K-line emission. As an X-ray flare brightens and fades, the gas follows in turn after a brief delay depending on its distance from the source.

"Direct light from the flare has different properties than its echo, and we can detect reverberations by monitoring how the brightness changes across different X-ray energies," said co-author Jon Miller, a professor of astronomy at the University of Michigan in Ann Arbor.

Swift J1644+57 is one of only three tidal disruptions that have produced high-energy X-rays, and to date it remains the only event caught at the peak of this emission. These star shredding episodes briefly activate black holes astronomers wouldn't otherwise know about. For every black hole now actively accreting gas and producing light, astronomers think nine others are dormant and dark. These quiescent black holes were active when the universe was younger, and they played an important role in how galaxies evolved. Tidal disruptions therefore offer a glimpse of the silent majority of supersized black holes.

Image above: Images from Swift's Ultraviolet/Optical (white, purple) and X-Ray telescopes (yellow and red) were combined in this composite of Swift J1644+57, an X-ray outburst astronomers classify as a tidal disruption event. The event is seen only in the X-ray image, which is a 3.4-hour exposure taken on March 28, 2011. The outburst was triggered when a passing star came too close to a supermassive black hole. The star was torn apart, and much of the gas fell toward the black hole. To date, this is the only tidal disruption event emitting high-energy X-rays that astronomers have caught at peak luminosity. Image Credits: NASA/Swift/Stefan Immler.

"If we only look at active black holes, we might be getting a strongly biased sample," said team member Chris Reynolds, a professor of astronomy at UMCP. "It could be that these black holes all fit within some narrow range of spins and masses. So it’s important to study the entire population to make sure we’re not biased."

The researchers estimate the mass of the Swift J1644+57 black hole at about a million times that of the sun but did not measure its spin. With future improvements in understanding and modeling accretion flows, the team thinks it may be possible to do so.

ESA's XMM-Newton satellite was launched in December 1999 from Kourou, French Guiana. NASA funded elements of the XMM-Newton instrument package and provides the NASA Guest Observer Facility at Goddard, which supports use of the observatory by U.S. astronomers. Suzaku operated from July 2005 to August 2015 and was developed at the Japanese Institute of Space and Astronautical Science, which is part of the Japan Aerospace Exploration Agency, in collaboration with NASA and other Japanese and U.S. institutions.

NASA's Swift satellite was launched in November 2004 and is managed by Goddard. It is operated in collaboration with Penn State University in University Park, the Los Alamos National Laboratory in New Mexico, and Orbital Sciences Corp. in Dulles, Virginia, with international collaborators in the U.K., Italy, Germany and Japan.